From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mail.netfilter.org (mail.netfilter.org [217.70.190.124]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id D38CE2EC086; Wed, 10 Jun 2026 16:16:40 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=217.70.190.124 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1781108202; cv=none; b=i0DzIT4ezvQp7QHqdaj8qET2mIO8ix2j4eWr33zPIUsBx2824nm4zi87gg+kJSanCutNy0Yb7HA3r74sWC+WsnqR6oSUPrTHP50r7sOFw6o7v/3e8oHEg3+EdTW0IsxM513wDxqsUxrYijkQzYwD+oLH7gKea65kfu6MTnZiwDE= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1781108202; c=relaxed/simple; bh=jCMwWxwZzghcErLFh01XEOuSNUxfLv8d/M/MacWh/B4=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=iYEYvmz8SL18kZV8N+jmh97kOhVsznkJLjN0CWz3ooK26BIKbkPQYtWpEfY0hU72stHJ/sAMG4JAfrf1l4L7SU4ANIJt6OeWaDAN1PROo7woA58B5/zxQ1GbSiN7ulaZjGbYHjgyIDZwHmHiK0CjrZ49voFAXVq+Z1sq+EqdVLw= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=none (p=none dis=none) header.from=netfilter.org; spf=pass smtp.mailfrom=netfilter.org; dkim=pass (2048-bit key) header.d=netfilter.org header.i=@netfilter.org header.b=tlSgqe+z; arc=none smtp.client-ip=217.70.190.124 Authentication-Results: smtp.subspace.kernel.org; dmarc=none (p=none dis=none) header.from=netfilter.org Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=netfilter.org Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=netfilter.org header.i=@netfilter.org header.b="tlSgqe+z" Received: from localhost.localdomain (mail-agni [217.70.190.124]) by mail.netfilter.org (Postfix) with ESMTPSA id 31127601BF; Wed, 10 Jun 2026 18:16:39 +0200 (CEST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=netfilter.org; s=2025; t=1781108199; bh=WZ1RWSb3R8vG0hIZiejwx1SegDXgikA48Oao5eS8LSc=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=tlSgqe+zGLPV4wv4tb6NU/H1xgdwzmdh4Ge4jHW4r0wJ2YAEXhPCzWupMlQvdx//c bsarVCk6svUpRGkiE39DFdA2E0KtyURAFRGnmxZl/W0F2lUPKxiVzhHxjoI1aj+O8R cR6ARPhqsTJz8Zf+qMpkuNXd64HawFSiDhSo11K7CSf52ZzL0cXq+U25G8S7yoCRUk UvINPqy2LPQOQf3BAw8F2J0MZ1/2gihMH520+WM2v+bylpfMVyfzmlLHq/yWSoex24 mn/C99SBoXqN4jCbZAnTYjy/CPwVTVC5syTwFG9O48U7iS0aeRLqj2ZFIouiWGTled 1pPDcF0zS8vZA== From: Pablo Neira Ayuso To: netfilter-devel@vger.kernel.org Cc: davem@davemloft.net, netdev@vger.kernel.org, kuba@kernel.org, pabeni@redhat.com, edumazet@google.com, fw@strlen.de, horms@kernel.org Subject: [PATCH net 5/8] netfilter: nf_log: validate MAC header was set before dumping it Date: Wed, 10 Jun 2026 18:16:25 +0200 Message-ID: <20260610161629.214092-6-pablo@netfilter.org> X-Mailer: git-send-email 2.47.3 In-Reply-To: <20260610161629.214092-1-pablo@netfilter.org> References: <20260610161629.214092-1-pablo@netfilter.org> Precedence: bulk X-Mailing-List: netdev@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit From: Xiang Mei The fallback path of dump_mac_header() guards the MAC header access only with "skb->mac_header != skb->network_header", without checking skb_mac_header_was_set(). When the MAC header is unset, mac_header is 0xffff, so the test passes and skb_mac_header(skb) returns skb->head + 0xffff, ~64 KiB past the buffer; the loop then reads dev->hard_header_len bytes out of bounds into the kernel log. This is reachable via the netdev logger: nf_log_unknown_packet() calls dump_mac_header() unconditionally, and an skb sent through AF_PACKET with PACKET_QDISC_BYPASS reaches the egress hook with mac_header still unset (__dev_queue_xmit(), which would reset it, is bypassed). Add the skb_mac_header_was_set() check the ARPHRD_ETHER path already uses, and replace the open-coded MAC header length test with skb_mac_header_len(). Only skbs with an unset MAC header are affected; valid ones are dumped as before. BUG: KASAN: slab-out-of-bounds in dump_mac_header (net/netfilter/nf_log_syslog.c:831) Read of size 1 at addr ffff88800ea49d3f by task exploit/148 Call Trace: kasan_report (mm/kasan/report.c:595) dump_mac_header (net/netfilter/nf_log_syslog.c:831) nf_log_netdev_packet (net/netfilter/nf_log_syslog.c:938 net/netfilter/nf_log_syslog.c:963) nf_log_packet (net/netfilter/nf_log.c:260) nft_log_eval (net/netfilter/nft_log.c:60) nft_do_chain (net/netfilter/nf_tables_core.c:285) nft_do_chain_netdev (net/netfilter/nft_chain_filter.c:307) nf_hook_slow (net/netfilter/core.c:619) nf_hook_direct_egress (net/packet/af_packet.c:257) packet_xmit (net/packet/af_packet.c:280) packet_sendmsg (net/packet/af_packet.c:3114) __sys_sendto (net/socket.c:2265) Fixes: 7eb9282cd0ef ("netfilter: ipt_LOG/ip6t_LOG: add option to print decoded MAC header") Reported-by: Weiming Shi Assisted-by: Claude:claude-opus-4-8 Signed-off-by: Xiang Mei Signed-off-by: Pablo Neira Ayuso --- net/netfilter/nf_log_syslog.c | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-) diff --git a/net/netfilter/nf_log_syslog.c b/net/netfilter/nf_log_syslog.c index 7a8952b049d1..e37b09b3203b 100644 --- a/net/netfilter/nf_log_syslog.c +++ b/net/netfilter/nf_log_syslog.c @@ -815,8 +815,8 @@ static void dump_mac_header(struct nf_log_buf *m, fallback: nf_log_buf_add(m, "MAC="); - if (dev->hard_header_len && - skb->mac_header != skb->network_header) { + if (dev->hard_header_len && skb_mac_header_was_set(skb) && + skb_mac_header_len(skb) != 0) { const unsigned char *p = skb_mac_header(skb); unsigned int i; -- 2.47.3